This invention relates to a surgical instrument commonly referred to as a trocar, or an obturator and cannula, often used in laparoscopic or arthroscopic surgery. More particularly, the invention relates to a reducer cap used in conjunction with a trocar cannula.
Many surgical procedures are now being performed with the use of trocars and cannulas. Originally these devices were used for making a puncture and leaving a tube to drain fluids. As technology and surgical techniques have advanced, it is now possible to insert surgical instruments through the cannulas and perform invasive procedures through openings less than half an inch in diameter. Previously these procedures required incisions of many inches. By minimizing the incision, stress, and loss of blood, the patients recovery times are dramatically reduced.
Surgical trocars are most commonly used in laparoscopic surgery. Prior to use of the trocar, the surgeon will usually introduce a Veress needle into the patient's abdominal cavity. The Veress needle has a stylet which permits the introduction of gas into the abdominal cavity. After the Veress needle is properly inserted, it is connected to a gas source and the abdominal cavity is insufflated to an approximate abdominal pressure of 15 mm Hg. By insufflating the abdominal cavity, pneumoperitoneum is created separating the wall of the body cavity from the internal organs.
A trocar is then used to puncture the body cavity. The piercing tip or obturator of the trocar is inserted through the cannula or sheath, and the cannula partially enters the body cavity through the incision made by the trocar. The obturator can then be removed from the cannula and an elongated endoscope or camera may be inserted through the cannula to view the body cavity. Surgical instruments may also be inserted to perform ligations or other procedures.
Once the cannula has been introduced into the opening in the body cavity wall, the pneumoperitoneum may be maintained by introducing gas into the abdominal cavity through the cannula. Various seals and valves have been utilized to allow abdominal pressure to be maintained in this fashion. Maintaining abdominal pressure is important both to allow working room in the body cavity for instruments introduced through the cannula, and to provide free space for the puncturing of the body cavity wall by one or more additional trocars as may be required for some procedures.
Endoscopic surgical procedures often require the use of surgical tools of varying diameters. Although trocars are provided in different diameters, some procedures will inevitably require the use of surgical tools with smaller diameters than that of the cannula. Converting the cannula's diameter rather than inserting separate cannulas for different surgical tool sizes reduces recovery time and the risk of surgical accidents. Where the diameter of the cannula must be converted to use smaller diameter tools, pneumoperitoneum must be maintained while converting the proximate opening of the cannula from a larger diameter to a smaller one. To maintain pneumoperitoneum during surgery, an airtight seal must be made around the smaller diameter surgical tools inserted into the larger diameter cannula.
A system which rapidly and efficiently reduces the diameter of the cannula while retaining pneumoperitoneum is necessary during endoscopic surgical procedures. Reducing systems are described in Stephens, U.S. Pat. No. 5,338,307; Wulf, U.S. Pat. No. 5,385,560; and Shichman, U.S. Pat. No. 5,104,383.
Reducer systems currently on the market consist either of a plate which must be slid into place or a cap which snaps onto the cannula housing. For instance, Shichman, U.S. Pat. No. 5,104,383, shows a sliding plate reducer system. This reducer system cannot be attached to the cannula before surgery, but only after the cannula has been inserted through the abdominal cavity wall and the obturator removed. This reducer system requires the surgeon to slide the plate on for smaller instruments used and back off to return to the original diameter of the cannula. Since the plate is not attached to the cannula, the diameter cannot be reduced as efficiently since the plate must be searched for during surgery.
Another system, described in Stephens, U.S. Pat. No. 5,338,307, consists of a reducer cap which snaps onto the cannula housing. This system consists of a base which attaches to the cannula housing, and a cap, containing a gasket assembly, which is attached to the reducer system base by a pin and hinge assembly. The cap is designed so surgeons can flip the cap to convert from one diameter size to another. Although this system does remain attached to the cannula during surgery, several disadvantages exist with Ethicon's reducer cap. For instance, because the cap latches to the base of the reducer system base, if the latch fails to release the surgeon may inadvertently remove the entire reducer system with attendant loss of pneumoperitoneum. Most significantly, this reducer system base attaches to the cannula using the same slots in the cannula that engage tabs from the obturator when the trocar is assembled for piercing the body cavity wall. The reducer cap can only be mounted in place after the incision is made and the obturator removed from the cannula.
Finally, with the current emphasis on cost controls in health care, the most cost efficient product should be utilized whenever possible. The pin and hinge assembly of Stephens, connecting the base and the cap entails higher costs due to the specially molded pieces and increased labor required to assemble the cap to the base. Therefore, a need exists for an attachable, cost efficient trocar reducer system which can be easily used while reducing the risk of mishandling the system during laparoscopic and similar surgical procedures.